tolong kerjakan tugas ini, pakai jalan

1a) y = x
disubtitusi
y + x = 10
x + x = 10
2x = 10
x = 5
disubtitusi
y = x
y = 5
hp = { 5,5 }

b) x = y + 5
disubtitusi
2y + x = 17
2y + y + 5 = 17
3y = 17 - 5
3y = 12
y = 4
disubtitusi
x = y + 5
x = 4 + 5
x = 9
hp = { 9, 4 }

c) y + 2x = 3
y = - 2x + 3
disubtitusi ke pers :
2y - 3x = 8
2(-2x + 3) - 3x = 8
- 4x + 6 - 3x = 8
- 7x = 8 - 6
- 7x = 2
x = - 2/7
disubtitusi
y = - 2x + 3
y = - 2(-2/7) + 3
y = 4/7 + 3
y = 4/7 + 21/7
y = 25/7
hp = { - 2/7 , 25/7 }

d) x - y = 3
x = y + 3
disubtitusi ke pers :
2x + 3y = 11
2(y + 3) + 3y = 11
2y + 6 + 3y = 11
5y = 11 - 6
5y = 5
y = 1
disubtitusi ke pers :
x = y + 3
x = 1 + 3
x = 4
hp = { 4 , 1 }

e) 3x - 2y = 3
3x = 2y + 3
disubtitusi ke pers :
6x - 2y = 8
( 2•3x ) - 2y = 8
2(2y + 3) - 2y = 8
4y + 6 - 2y = 8
2y = 8 - 6
2y = 2
y = 1
disubtitusi ke pers :
3x = 2y + 3
3x = 2(1) + 3
3x = 5
x = 5/3
hp = { 5/3 , 1 }

2a) misal
panjang = x
lebar = x - 10
K = 2 × ( p + l )
80 = 2 × ( x + x - 10)
80 = 2 × ( 2x - 10)
2x - 10 = 80 ÷ 2
2x - 10 = 40
2x = 40 - 10
2x = 30
x = 15
jadi
panjang = x = 15 cm
lebar = x - 10 = 15 - 10 = 5 cm